1. Field of the Invention
The present invention relates generally to a method and apparatus for detecting drive line system imbalances. More specifically, the present invention relates to a method and apparatus for detecting system imbalances in a drive line assembly for an automotive vehicle using non-contacting vibration sensors.
2. Description of the Related Art
Generally speaking, automotive vehicles require three basic components: a power plant, such as an internal combustion engine, a drive line system or drive train, as it is sometimes known in the art, and a plurality of rotatably driven wheels. A typical drive line system may include a transmission, a drive shaft and an axle connected between the engine and the driven wheels. Engine torque and speed are converted in the transmission in accordance with the tractive-power demand of the wheels and translated to the drive shaft. In turn, the drive shaft transmits rotational power from the transmission to the driven wheels via the axle assembly. The axle assembly includes a differential which is operatively coupled to the drive shaft through a pinion nose. A pair of output axle shafts connect the differential to the driven wheels.
The drive shaft typically includes an elongated tubular member which is operatively coupled to the transmission and axle assembly through a pair of universal joints or other similar coupling disposed on either end of the shaft. Alternatively, the drive shaft may include two or more elongated tubular members which are connected together by a universal joint or some other similar coupling device and connected between the transmission and axle assembly as above-discussed. Additionally, a center bearing is often employed between the transmission and axle assembly to support the drive shaft relative to the body of the vehicle.
The individual components of the drive line system discussed above often include inherent or residual imbalances due to variations in manufacturing tolerances. While steps can be taken to balance the individual components, residual imbalances often still remain. When the individual components are assembled into the drive line system, the residual imbalances can "stack up" such that they combine to produce a relatively high level of imbalance. Automotive drive line systems which embody these characteristics are unacceptable because they produce drive line vibration and boom.
It is known in the related art to balance the drive line system prior to installation into the vehicle. Many fixtures are known in the art for performing this function and typically rely on vibration measuring devices physically coupled to the drive line system to identify and thereafter correct the imbalances.
Still, this is often not enough to eliminate objectional vibration in the drive line system of a fully assembled automotive vehicle. Thus, devices have been proposed in the related art which seek to identify and correct drive line system imbalances at the terminal stage of vehicle production and prior to shipment of the vehicle. However, these devices suffer from the disadvantage that an additional step in the manufacturing process must be added in order that vibration sensing instrumentation can be physically coupled to the drive line system of each vehicle. This is time consuming and labor intensive. In short, drive line system balancing as employed in the related art for a fully assembled automotive vehicle is presently not cost effective.
Accordingly, there is a need in the art for an apparatus which can detect and perform drive line system balancing in a fully assembled automotive vehicle in high volume production environments which is transparent to the current workload. More particularly, there is a need in the art for an apparatus for performing drive line system balancing which does not rely on the physical attachment of vibration sensing instrumentation to the automotive vehicle in order to detect and correct system imbalances.